LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 2B: EMISSIONS MODELLING 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Table 1. Shares of emission sources in potato case when using IPCC 2006 default emission factor and the
new national method.
IPCC 2006 New national method
N2O emissions from managed soils 16% 32%
Other GHG-emissions from cultivation 38% 36%
Processing, packaging, transport 46% 36%
Total kgCO2-eq./kg potato product 0.11 0.13
Comparisons between the new national method and the IPCC 2006 method were also made at national level.
Applying the new national method, direct nitrous oxide emissions from applied nitrogen from managed mineral
soils increased approximately by 100% compared with the IPCC 2006 method, depending on the fertiliser
level assumed. The emissions from perennial crops decrease 30-46%, as emissions from annual crops
increase by 232-250% (Table 2). The comparison shows that application of the new national method will
increase the estimated national direct nitrous oxide emissions significantly.
Table 2. Estimated change in national nitrous oxide emission levels from applied N in mineral soils when the
new national method is used instead of the IPCC 2006 method, with estimated minimum and maximum Finnish
fertiliser levels.
Minimum fertiliser levels Maximum fertiliser levels
Annual crops +250%
+232%
Perennial crops -46%
-30%
Others +176%
+164%
Total +116%
+99%
4. Discussion
It is known that many factors in addition to fertiliser application rate have an effect on nitrous oxide
fluxes. Several of these factors were also studied in long-term field measurements in Finland, such as type of
fertiliser (mineral/organic), percentage of organic carbon, sand and clay in the 0-20 cm soil layer, mean temperature
for the winter months (Jan-Mar) and total precipitation for the summer months (May-Sep). However,
inclusion of the other parameters did not improve the performance of the models. This is a clear drawback
as the models cannot take into account diverse cultivation methods or mitigation options, such as organic
agriculture, autumn sown crops, reduced tillage etc.
The results indicate that the most important factor determining the annual flux of nitrous oxide is the type
of crop, based on the division between annual and perennial crops. It seems justified to add this dimension
also to the climate impact calculations for different agricultural products. The division is particularly important
for Finnish conditions where spring-sown crops prevail and where the period when the soils are not covered
by crops can be close to nine months. This increases the incidence of nitrous oxide emissions from these
soils.
5. Conclusion
The new national method provides realistic estimates of nitrous oxide fluxes under boreal conditions,
characterised by frozen soils in the winter, frequently renewed grasslands, and spring-sown annual crops.
The more accurate method highlights that under boreal conditions, such as Finland, direct nitrous oxide
emissions from annual crops on mineral soils are markedly higher than suggested by the IPCC method. It
also demonstrates that total Finnish direct nitrous oxide emissions from all managed soils are likewise
higher.
Acknowledging the substantial variation in nitrous oxide emissions, developing new methods to estimate
fluxes in more detail should be given much more attention. Better knowledge of food production in different
climates is needed. As interest in climate impacts of food grows, the need for more detailed assessment
methods is urgent.
6. References
Australian national greenhouse accounts, 2010. National Inventory Report 2010. Vol. 1. The Australian Government Submission to
the United Nations Framework Convention on Climate Change April 2012
Barton, L., Kiese, R., Gatter, D., Butterbach-Bahl, K., Buck, R., Hinz, C., Murphy, D.V., 2008. Nitrous Oxide Emissions from a
Cropped Soil in a Semi-Arid Climate. Glob. Change Biol., 14, 177–192.
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